Daattaasshheeeett
BM2PXX2F
(3) VCC pin protection function
BM2PXX2F built in VCC low voltage protection function VCCUVLO (Under Voltage Lock Out), over voltage protection
function VCC OVP (Over Voltage Protection) and VCC charge function that operates in case of dropping the VCC voltage.
VCC UVLO and VCC OVP monitor VCC pin and prevent VCC pin from destroying switching MOSFET at abnormal
voltage.
VCC charge function stabilizes the secondary output voltage by charging from the high voltage line by start circuit at
dropping the VCC voltage.
(3-1) VCC UVLO ／ VCC OVP function
VCCUVLO is auto recovery protection. VCCOVP is auto recovery protection. And they have voltage hysteresis. Refer to
the operation figure-8.
Switching is stopped by the VCCOVP function when VCC pin voltage > Vovp1 (typ=27.5V), and Switching is restart when
VCC pin voltage < Vovp2 (typ=23.5V)
VH
VO
VP1
Vovp1=27.5Vtyp
VOVP2
Vovp2=23.5Vtyp
VCC
VUVLO 1
VCCuvlo1=13.5Vtyp
VC
HG2
Vchg2=13.0Vtyp
VCHG1
Vchg1=8.7Vtyp
VUV =
LO2
VCCuvlo28.2Vtyp
Time
ON
ON
OFF
VCC UVLO
VCC OVP
ON
OFF
OFF
ON
ON
VCC Charge
Function
OFF
ON
OUT
OFF
Switching
OFF
Time
A
B C
D
F
I
J
A
E
G
H
Figure 8. VCC UVLO / OVP Timing Chart
A: DRAIN voltage input, VCC pin voltage starts rising.
B: VCC>VUVLO1, DC/DC operation starts
C: VCC< VCHG1, VCC charge function operates and the VCC voltage rises.
D: VCC > VCHG2, VCC charge function is stopped.
E: VCC > VOVP1, continues TLATCH (typ =100us), switching is stopped by the VCCOVP function.
F: VCC < VOVP2, Switching operation restarts
G: VH is OPEN.VCC Voltage is fall.
H: Same as C.
I: Same as D.
J: VCC<VUVLO2, Switching is stopped by the VCC UVLO function
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TSZ22111・15・001
TSZ02201-0F2F0A200040-1-2
7. Mar.2017.Rev.007
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